Hey, I can see the light at the end of the tunnel on this project. Of the ten total pieces for the job, seven have been installed and three need to be placed.
If you haven't tried lithium silicate densifier, get a gallon and give it a shot. It basically increases the degree of hydration at the surface to make the concrete harder and less porous. I've used these on pavements for a number of years, but when you actually put it on by hand you can feel the concrete tightening up. I have been doing two applications at 50% strength, letting it sit for a day, and then two applications at full strength. They tend to slightly darken the surface which helps bring out the color.
I haven't been forming holes for faucet on these. I think it is easier to cut cut them in later. I bought a cheap diamond hole saw set at Harbor Freight for like $10 which works well enough.
A few installed and the sink getting siliconed to the bottom.
The bathroom sinks are a basin that just sits on top.
After applying the densifier I then have been applying a few coats of silane. I have been playing around with application techniques for the silane water proofer. This is after cutting it with some water and buffing lightly with a mild abrasive pad.